Trends of 13C/12C Ratios in Pinyon Tree Rings of the American Southwest and the Global Carbon Cycle
AuthorLeavitt, S. W.
C 13 C 12
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CitationLeavitt, S. W., & Long, A. (1986). Trends of 13C/12C ratios in pinyon tree rings of the American Southwest and the global carbon cycle. Radiocarbon, 28(2A), 376-382.
PublisherAmerican Journal of Science
DescriptionFrom the 12th International Radiocarbon Conference held in Trondheim, June 24-28, 1985.
AbstractAn accurate atmospheric 13C/12C chronology can provide important constraints to models of the global carbon cycle. Trees accumulate carbon from atmospheric CO2 into growth rings and offer potential for 13C/12C reconstructions, but results have not been reproducible. This paper presents 5 degree C curves from 5 sites, representing 20 pinyon (Pinus edulis) trees, where cores of 4 trees from each site have been pooled into a composite sample. Isotopic analysis of cellulose in 5-yr ring groups produces curves with a general trend of decreasing 5 degree C after 1800, but with pronounced short-term fluctuations superimposed upon the trend. Evidence indicates the fluctuations are strongly related to moisture availability (drought). A mean curve of the 5 delta-13C chronologies from which the fossil-fuel component is subtracted suggests a substantial biospheric CO2 contribution to the atmosphere since 1800.